Japanese Patent Application Publication No. H07-115307 and Japanese Patent Application Publication No. H04-122581 disclose a battery-powered fastener-driving tool. The fastener-driving tool uses the driving force of a motor to raise a plunger, compressing a coil spring. When the coil spring is released, the plunger accelerates to drive a fastener.
This fastener-driving tool uses the rotation of a motor to compress the coil spring, storing the energy of the spring. When the coil spring is released, the plunger and a driver blade mounted thereon are rapidly accelerated, and the driver blade strikes a fastener. After impact, the plunger collides with a bumper that absorbs the excess energy, halting the plunger and driver blade. During this operation, the driver blade ejects a prescribed distance out through an opening in the main body of the fastener-driving tool to drive the fastener into a workpiece.
Here, there is a need for the fastener-driving tool to be capable of adjusting the depth at which the fastener is driven into the workpiece, hereinafter referred to as the “driving depth,” because the fastener-driving tool may be used on workpieces formed of various materials. Depending on the material composition of the workpiece, the fastener may not be completely embedded in the workpiece or may be driven too far into the workpiece if the fastener-driving tool strikes the workpiece with a fixed force of impact. Therefore, some conventional fastener-driving tools have been provided with a mechanism for adjusting the driving depth.
Japanese Patent Application Publication No. H04-122581 discloses a mechanism for shifting the bumper in the direction that the fastener is driven (hereinafter “driving direction”) or in the direction opposite the driving direction. This fastener-driving tool is provided with a bumper holder for supporting the bumper in the housing. The bumper holder is capable of moving integrally with the bumper in the driving direction or the direction opposite the driving direction. A rotatable adjuster is provided in the housing. A threaded part is formed on part of the bumper holder, and another threaded part is formed on a portion of the adjuster and is screwed together with the threaded part of the bumper holder. A peripheral portion of the adjuster is exposed outside of the housing through a through-hole formed in the housing.
The user can adjust the positions of the bumper and bumper holder in either the driving direction or the direction opposite the driving direction by rotating the adjuster. When the user adjusts the position of the bumper in the direction opposite the driving direction, the plunger more quickly impacts the bumper during a driving operation, reducing the driving depth. Conversely, when the user adjusts the position of the bumper in the driving direction, the plunger impacts the bumper later during a driving operation, increasing the driving depth.
This fastener-driving tool is also provided with an anti-rotating mechanism to prevent the adjuster from unexpectedly rotating when there is no need to rotate the adjuster. Specifically, a plurality of recessed parts is formed circularly in one axial endface of the adjuster, while a pin whose head part can contact one of the recessed parts is urged toward the adjuster endface by a spring. With this construction, the pinhead engages in one of the recessed part when the adjuster is rotated, producing a clicking sensation and preventing the adjuster from rotating in a smooth, continuous motion. Thus, the engagement of the pin in one of the recessed parts prevents the adjuster from rotating unexpectedly.